Corrugated pipe sections are used in the drainage of water-saturated soil in various agricultural, residential, recreational, or civil engineering and construction applications, such as for storm sewers. Traditionally, drainage pipe was made from clay or concrete, which caused the pipe to be heavy, expensive, and brittle. In order to improve the cost-effectiveness, durability, and ease-of-installation of drainage pipes, it is now common in the art to manufacture them from various materials including various polymers and polymer blends.
Such plastic drainage pipe is generally extruded, molded, and cut to form relatively light, manageable, and transportable sizes of drainage pipe sections, ranging from a few feet to many yards in length. Once these plastic pipe sections are transported to their desired installation location, they are assembled lengthwise by the installation of joints, adhesives, or other coupling means. This coupling process has generally been complex, requiring the transportation of many tools and supplies to the job site, and has required many man-hours for completion.
For example, one method of assembly involves the formation of a wide-diameter bell at one end of each plastic pipe section. During the pipe manufacturing process, an apparatus known as a “beller” is used to radially expand the end of the pipe, forming an expanded bell-shaped structure, such that the opposite end of an adjacent pipe section may be inserted into the expanded bell-shaped end. This process has several disadvantages.
First of all, these pipe bells are generally weakened during their expansion and require additional means of reinforcement, such as external straps, hinged brackets, overlapping wraps, shrink-wrap layers, or a combination of such reinforcement means. In some instances, more material must be used at the pipe bell ends to compensate for reduced strength, thereby increasing weight and expense. Moreover, because the pipe bells are expanded to diameters larger than the central portion of the pipe, it becomes necessary to dig trenches that can accommodate the larger bell. Finally, these bells and other known coupling means require precise and careful excavation, installation, and backfill, to avoid misalignment between pipe sections during assembly and placement. The improper installation of these coupling means often results in joint failure, buckling, and an inability to form a water-tight seal between adjacent pipe sections.
The above problems, which are known to exist in relation to single- and dual-wall pipe, can be even more troublesome in three-wall pipe applications. For example, it may be substantially more difficult and expensive to form a bell-shaped end on a section of three-wall, corrugated pipe, due to increased material weight and stiffness.
Accordingly, there is a need for an improved water-tight, in-line, bell and spigot, which can be used for coupling sections of three-wall, corrugated pipe.